1. Field of the Invention
This invention relates to a chamfering machine for effecting burring or chamfering of cut end surfaces of an elongate metal material of circular cross-section such as a bar or a tube.
2. Related Background Art
When an elongate metallic round bar or tube continuously manufactured is cut to a predetermined length, burr or the like sticks to the cut end surfaces thereof and therefore it need be removed. This burring is accomplished as by pushing the cut end surface of the elongate bar material against a rotating grind stone and rotating the bar material, whereby the bar material has its end edge smoothly ground concentrically.
The force with which an elongate "round bar material" (it is to be understood that this term covers a bar and a tube having a circular cross-section) is pushed against a rotating grind stone must be chosen to a predetermined magnitude, and must not be too strong or too weak. Further, the end edge of the round bar material need be ground over its full periphery and therefore, simultaneously with the pushing force, a rotational force must be imparted to the round bar material.
Heretofore, such a kind of work has been difficult to mechanize, and even mechanized works have hardly satisfied the subtle force relation required. Among the examples of the prior art, the chamfering machine proposed by the applicant (Japanese Utility Model Registration No. 1394371 (German Patent DE No. 2921345C2)) is an example which has overcome the difficulty in mechanization.
In the above-mentioned applicant's chamfering machine, a plurality of rollers of a conveying device for longitudinally conveying an elongate round bar material (conveying a round bar material in the lengthwise direction thereof) are disposed obliquely with respect to the axis of the conveying device. These obliquely disposed rollers are adapted to cooperate with a conveying device for laterally conveying the round bar material and a rotating grind stone to act. That is, when the obliquely disposed rollers are rotated, a force which pushes the round bar material lying thereon in the lengthwise direction thereof and a force which induces the rotation thereof are imparted to the round bar material by friction. By the cooperation of these forces with the laterally conveying device and the rotating grind stone, the end portion of the round bar material is rotated and laterally conveyed while being pushed against the rotating grind stone and thus, burring and chamfering of the end surface is accomplished.
The operation of chamfering the end portion of the round bar material by the machine of the above-mentioned Japanese Utility Model Registration No. 1394371 has suffered from the following disadvantages and has left room for improvement. Where as in the above-described machine, a round bar material is moved by obliquely disposed longitudinally conveying rollers and a transfer conveyor having the dogs of a laterally conveying device, if the longitudinally conveying rollers and the laterally conveying transfer conveyor are installed generally horizontally or downwardly sloped, the round bar material has sometimes run away from the dogs and rolled when it is laterally conveyed by being pushed by the dogs.
Also, in the above-described machine, the longitudinally conveying rollers are disposed in two rows and between these rows of conveying rollers, there is an intermediate conveying roller for aligning the round bar material in the lengthwise or longitudinal direction thereof and moving it to chamfer the both end surfaces of the round bar material in succession. During the longitudinal movement of the round bar material by this intermediate conveying roller, the round bar material is moved in a direction perpendicular to the movement of the dogs while being in contact with the dogs of the laterally conveying device. Accordingly, if the dogs are merely fixed fittings such as short posts, the end portion of the round bar material may collide against them.
Further, if the dogs are of the fixed type, when the dogs contact with the round bar material and laterally conveys the latter, the friction between the two is great and therefore, forward rolling of the round bar material is liable to occur.